Hi Chris

Sorry for this inordinate delay. I couldn't upload the attachments on Friday and I didn't have access to this data at home, so didn't make the post then.

Here it is now though.

In the attachment, I have included the query that I ran, the result sets, the statistics data and the actual execution plans for both the options as requested by you, the first without the last where clause and the second with it. This time around, it didn't take anywhere near as long as it did earlier although I did replace the derived table 'b' with your '...partition by... clause for both the queries of the overall union query. May be that was what was bringing it down with the where clause.

As I have said earlier, I dont't know how to read the execution plan as yet (I am going to be spending time soon to be able to understand at least the very basics of it so that I can write slightly more efficient queries this point forward), but I am sure it would tell you a lot and you would be able to intrepret the same and advise as to where it was falling down.

Shall look forward to hearing from you soon.

Once again, sorry for not providing you with the relevant details earlier.

Best regards

Deepak

I will test with your revision later tonight and advise.

Deepak